I didn't vote, because the original question, in my opinion, doesn't quite cover the topic. The term "nice guy" is little more than a social/cultural construct and it implies a certain objectivity that doesn't seem to have much to do with what this is all about. It's much more subjective than that. For me, "nice" takes second place to things like "sympathetic", someone I can identify with and feel sympathetic towards in a much more subjective manner. We can all watch the same interviews and the same races and come out with a hundred different views of just what we saw. It has more to do with us, individually, than with the riders in question.
As for Contador... He might be a liar. He might not be. Some of the things he's said and done point in the direction of him not always having the closest relationship with honesty. Does that make him less sympathetic to me? No. When I get backed into a corner, I'll say whatever I think will get me out fastest. When I'm in a tight spot, I'm a bit of a coward. Would I call myself a pathological liar? No. Am I, occasionally, a liar? Fvck yes. It's not something I'm particularly proud of, but that's how it is. It's not all I am, though. It's not all that defines me. I'm also empathic and creative and passionate and a million other things. Every personality in the world has many facets. That's what makes people interesting.
As Christian said some posts ago, a complete and total perfect automaton is ultimately boring. I agree with that completely. What I don't agree with is casting Contador in the role as "perfect". He's not, obviously. He seems to be a bit of a liar, sometimes, and a bit of a coward when he's put on the spot. That doesn't make him bad in my eyes. It makes him human. And for me, because these are weaknesses I see in myself, it makes him someone I can easily identify with. What takes him the next step to someone I can also admire is the fact that he also appears to have some traits I truly respect. Unlike others, he doesn't tend to use his illness as an excuse. He's a fighter. He never gives up. The combination of being able to see myself in his weaknesses and admiring his strength is really what makes him someone I want to root for.
Schleck on the other hand... human and flawed as well, quite obviously. Maybe he's the one I'd have identified with more back when I was a teenager, because I also did stupid sh!t and spewed all sorts of nonsense I hadn't thought through beforehand. I grew out of that, however, and that makes it harder for me to like him than it probably would've been when I was younger. Again, subjective and different for every single person.
Of course, on the other hand, popularity is ALSO a social/cultural construct. We see it with the Dutch and Belgian and British (and others; these are just examples) posters who loudly root for their compatriots. We see it in Denmark, where I'm from, where, to fifty per cent of cycling fans a couple of years ago, Contador was the villain standing in the way of Riis's next Tour de France triumph and Schleck was Riis's champion and the white knight who could do no wrong (probably didn't hurt that he has blond hair and blue eyes). Then Leopard TREK happened and those same fifty per cent grew a grudge the size of China and turned to the new champion. Of course, those same fifty per cent are just as prepared to extend the same grudge to Contador if he leaves Riis neck deep in sh!t and doesn't come back to help pull him out. In a case like that, the sympathy is not given to Contador or Schleck as individuals, but to them as extensions of Riis, on a nationalistic basis.
My point is that to be able to answer the original question, we first have to agree on who the "nice guys" are, and I doubt that will ever happen. Who we root for is too individual, too subjective, has too much to do with who we see little pieces of ourselves in.
For me, well, in a case of the wolf and the sheep, I'm going to root for the wolf. The wolf is not necessarily "bad", it simply understands the rules of the game (and in my opinion, the sheep are often TSTL anyway).
And now that I've spent my first ever post boring you all to death and painting myself in the worst light possible, I think I'll just go back to lurking.